Method of developing multilayer color films



Jan. 20, 1953 A. K; SCHWERIN 2,525,215

METHOD OF DEVELOPING MULTILAYER COLOR FILMS Filed March 29, 1950Patented Jan. 20, 1953 UNITED STATES rarest Andre Kurt Schwerin,

assignor to Miraccl-R Ltd,

Canada Montreal, Quebec, Canada,

Montreal, Quebec,

Application March 29, 1950, Serial No. 152,629

5 la ms This invention relates to the art of-- colour photo raphy d.more p rt l to t e positive reproduction of coloured images directlyonto sheets of opaque material coated with multilayer mulsions ommo lyref to a integral tripack.

The principal object of this invention is to make direct colour printsof the photographed obiect. without the employment .of intermediate neative or positive colour transparencies.

A further object is to provide a novel colour developing process for themulti-layer emulsion coated print material which will develop a highemulsion speed or high sensitivity in the emulsion.

A particular advantage ofmy colour developing process is that theemulsion coated. print material may now be directly subjected to highspeed exposures and then processed to produce a high degree ofsensitivity in the emulsions.

Another advantage is that a h gh colour reproduction fidelity can beattained by subjecting the pr o my developi pro ss- A further advantageis that the processing time, with the employment of mydevelopingprocess, is greatly reduced.

A still further advantage is in a new developing process which rendersexcellent half-tones without any colour fog.

A still further advantage is that my new developing process renders thecolour transparency films obsolete, thereby greatly reducing the cost ofcolour photography.

It is common practice in the art to reproduce colour prints directlyonto multilayeremulsion print material. But insofar as I am aware, thishas only been accomplished with the employment of an intermediate colourtransparency which serves to translate to the print material the colourimage absorbed by the transparency from the original image throughphotographic exposure to sa d im ge- The print material employed in thereproduction of colour prints has an opaque base of a cellulose acetate,or nitrate derivative which is coated with a multi-layer emulsionconsisting has al y of. ree s rimposed aye s o light temu si ns of wellknown silver halide co cos ion Th emulsion co st u i th rea ayer issensitised to bluish l h b th Canada March 3, 1 950 introduction of ablue sensitive colorant such as oxopseudocyanine. The emulsionconstituting the.

middle layer is sensitized to greenish light by the introduction of agreen sensitive colorant such as 5 pseudocyanine and the emulsionconstituting the lower layer is sensitized to reddish light by theintroduction of a red sensitive colorant such as carbocyanine. Thecolorants listed above are only given by way of example. These colorantswere selected from an extensive list ofcolorants given in a standardtext book. The colorants above selected are known to have the desiredproperties but there are other Well known colorants in the list whichhave the desired properties in equal or lesser degrees and therefore maybe substituted for the selected colorants. The emulsions haveincorporated therein non-diffusing colour formers or couplers inalcoholic solutions. These non-diffusing colour formers serve to combinewith oxidation products of a color developer of well known constituentshaving, for example, a hydrochloride salt ofdi-ethyl-paraphenylendiamine to form insoluble dyes when the sheet orfilm is subjected to a colour print developing process. The colourformer employed in the blue sensitive emulsion may be, for example, analcoholic solution of di-(benzoyl-acetic-acid) benzidine, forming ayellow dye. The colour former employed in the green sensitive emulsionmay be, for example, an alcoholic solution of1-.-(parastearyl-amino-phenyD-3 methyl-5 pyrazolene, forming a red dye,and the colour former employed in the red sensitive emulsion may be, forexample, an alcoholic solution of di-(l-oxy-Z- naphthoyl) benzidine,forming a blue dye.

The multi-layer emulsion print material has been in commercial use inthe trade for printing from colour transparencies and are readilyvidentifiable by persons in the trade according to their trade names.Several manufacturers are engaged in the production of the printmaterial and although the exact formulae for producing them remain atrade secret, they all contain the basic ingredients outlined above, ortheir equivalents. However, since this invention is not concerned withthe-production of the multi-layer emulsion print material but ratherwith the em ployment of these commercial products in a novel 50 manner,it is thought that the above description type of camera employed.Normally,

3 of their basic ingredients will be suflicient for those skilled in theart to identify them.

As previously stated, the conventional colour print on the multi-layeremulsion print material is produced from colour transparencies. Thesetransparencies generally have a high degree of colour or tone contrastranging from 2.0 to 3.0. Consequently, the gradation of the multi-layeremulsion print material must be very slow. The

sensitivity of this print material is also slow. A

That is to say, the light exposure of the colour transparency to thecoated material must be for a relatively long period of time to permitthe layers of emulsion to properly absorb the correct amount of colourfrom the transparency so as to reproduce as closely as possible theactual colours of the original photographed image.

By conventional processing or development of this coated print materialafter the image has been reproduced thereon the normal speed orsensitivity of the emulsion on the material is about the same as amedium bromide paper, that is, about 3-4 American Standards Association.Thus, it will be seen that such a low emulsion speed or low sensitivityis not normally receptive to high speed exposures. If one were to exposesuch a coated print material directly, even with prolonged exposure timeand to process it by ordinary known formulae, 1. e., those published byvarious photographic manufacturers, one would obtain a picture resultwhich would be nearly black. In prolonging the time of the bath in thefirst developer for as much as two hours, the multi-layer emulsionprints show an intense bluish or greenish colour fog. And, of course,with direct photographing, the pictured image, such as it is, will belaterally reversed.

The manner in which the present invention overcomes all of the abovedisadvantages will be more readily understood from the followingdetailed description, reference being had to the accompanying drawing inwhich- The single figure represents digrammatically a prism according tomy invention positioned before a camera lens.

My primary concern has been to devise a means whereby a colour image maybe photographed directly onto a multi-layer emulsion print material ofthe character above described by exposure of said print material whichis enclosed in any conventional camera to the colour image. The materialmay be arranged in camera in any conventional manner, for example, as asingle exposure print or may be in the formof a plurality of prints on aroll, depending on the the image produced would be laterally reversed.However, to correct this, optical adjustment is required. This isaccomplished by mounting a prism 5 before the lens 6. The prism ismounted in such a way that its base 7 is parallel to the optical axis ofthe lens in a position to obtain the maximum angle of deviation. Thus animage before the camera will have one side designated A reflected offthe prism base at point X to appear before the lens 6 in the lateralreverse position indicated A. Similarly the other side of the imagedesignated B will be reflected off the prism base at point Y to appearbefore the lens in the lateral reverse position indicated at B.

The lens will then laterally transpose the image portions designated Aand B so that the resultant image on the multi-layer emulsion printmaterial will correspond to the original image.

The prism employed in my invention is of a transparent plasticcomposition such as polymers of methyl methacrylate, which is colouredthroughout with a yellowish-brown dye of a type which is non-soluble inwater, non-fading and is suitable for chromatic correction. Such acoloured prism can be made suitable for lights of different colourtemperatures such as sunlight, photo flood, flashlight, etc.

It is often desirable to produce sharper chromatic definition tocompensate for different colour temperatures and chromatic variations ofthe print material. This is normally accomplished by placing colouredgelatine filters before the lens. To accomplish the best results theprism is divided in two, as indicated at 8, so that a filter 9 may bevertically positioned between the two halves of the prism to interceptoptical paths of the image passing through the prism. A conventionalfilter disc with a plurality of filters for different compensationsarranged thereon may be mounted for rotation in any suitable manner toposition any selected filter thereon between the prism halves in theoptical paths of the image.

After exposure to a colour image, the multilayer emulsion print materialis then removed from the camera and is subjected to my developingprocess. The processing, which is of prime importance to this invention,introduces above all a new formula for the first developer whichproduces a very high increase of emulsion sensitivity, permittingexposure times equal to or shorter than those used with the employmentof the conventional colour transparencies. For example, the speedcalculated in A. S. A. degrees, for outdoor picture taking, is about 32A. S. A. and for indoor picture taking, with photoflood lamps of 3400Kelvin, is about 25 A. S. A. With photofiood lamps and a light levelabout 720 foot candles, pictures can be taken directly with a lensaperture of :6.8 at an exposure time of one-tenth of a second. Outdoorpictures can be taken in sunlight with a lens aperture of fz8 at anexposure time of one twenty-fifth of a second.

To obtain this high emulsion speed the composition of the formula of thefirst developer is listed herebelow, giving specific quantities in theleft hand column with variations in the right hand column, as follows:

Water cc 1,000

Sodium sulphite grams 50 :25 Hydroquinone do i5 Sodium thiocyanate do3.0 0.5 Potassium bromide do 3.5 1.0 Sodium hydroxide do 50Benzotriazole do.. 0.75 iO.1 Ascorbic acid do 0.75 -v-0.1 Sodiumsulphate do 15 +10 The formula will have a pH value of 12.4.

The variation of the quantity of any ingredient will bear, for the mostpart, a relation to the variation of the quantities of certain otheringredients.

The sodium hydroxide in the above mentioned proportion acts as a strongaccelerator which produces a complete first developing in about sixminutes at a temperature of F. but in the conventional formulae thesodium hydroxide at the elevated temperature of the base normallyproduces two inconveniences. First, the softening of gelatine; second,intense colour fog. To reduce the softening of the gelatine, thequantity of sodium sulphite, which, in the conventional formulae isabout grs is reduced in the pres ent formula. Thus the oxidationproducts of my tralized have. the property of ee atine tann ncounteracting the soitenin effect'o the alka i- The developing substancein the above formula is hydro-quinone, but this substance can bereplaced by, for example, para-aminophenol. or other reducing substancesgiving an elevated contrast necessary by reason of the soft gradation ofthe utilized material.

The formula also contains a solvent for the silver halide composition,such as silver bromide, in a relatively elevated quantity, said solventbeing the sodium thiocyanate.

The principal difiiculty in processing the multilayer emulsion printmaterial when a photograph is taken directly thereon, consists of aheavy bluish or greenish colour fog which is produced by thedecomposition of a small quantity of noninsulated silver bromide in thedifferent emulsion layers. To decrease this fog, I have addedarelatively highquantity of potassium bromide to the first developer.(In theconventional de.- velopin processes the "complete disapp n ofcolour fog has ordinarily-been obtained by the addition of one or more.organic compounds like paramitrobenziminazol, orother well knowncompounds.) However, theseorganic compounds are not s ufiicient toproduce. desired results in my formula.

In my formula, I use a mixture of benzotriazole and ascorbic acid.Experience shows that the proportionate quantities given in this'formulaare a decisive factor. Equal portions of 0.5 gram per 1.000 on ives onlyind cisive results, but with approximately 0.75 gram each per 1000 co.the colourfog is completely obliterated. By increasing the quantities ofthe above men.- tioned mixture the result stays the same. but thesensitivity of the emulsion is rapidly decreased in proportion to the.excess quantities. Thus, the critical quantities of this added mixturewill be 0.75 gram each per 1000 cc. At this concentration, the speed ofthe emulsion will not be affected. The mixture may, however, vary inproportions to the extent of $0.1 providing that the total quantity is1.50 grams approximately, without substantially affecting the antifogproperties or the sensitivity of the emulsions.

After the processing in the first developer, the multi-layer emulsionmaterial often shows certain dichroic fog produced by the solvent actionof the sodium hydroxide on the silver halide composition. To preventthis kind of fog, the above formula contains an inert substance such assodium sulphate or the like which does not enter into the developingaction, but which tends to coagulate the colloidal silver as it forms.

The emulsion sheet is processed in the first developer mentioned abovefor six minutes at 80 F. and is then introduced in a stop bath (forexample, citric acid, 35 grams per 1000 cc.), and washed for one minutein a translucent tank, permitting at the same time the second exposure.After this, the sheet is processed for 6 minutes at 80 F. in a colourdeveloper of known constituents, for example, hydrochloride salt ofdi-ethyl-paraphenylen-diamine. There are other colour developerscontaining, for example, 2- amino-5-diethyl aminotoluene These are,however, well known in the art, and form no part of this inventionbeyond the necessity of employing any suitable colour developer in thecompletion of the printing process after the print has been subjected tomy first developer process. The print is then introduced into achlorhydrate.

new stop bath, washed. and the. silver image fonned'is subsequentlyremoved by Farmer educer solution which the formed silver bro---ventional developing processes in which the first developer calls forimmersion periods of from 60 to 90 minutes. Myprocessing can be done byhand or by an automatic developing machine.

From the foregoing it will be appreciated that, with the exception ofthe water, benzotriazole and ascorbic acid, the quantities of theingredients should preferably be increased or .decreasedproportionately. Or, if' not increased proportionately, certain factorsmust be taken into consideration. The sodium hydroxide must be in aproportion which at R, will serve as a strong accelerator. The sodiumsulphite must be in a proportion which when combined with thehydro-quinone will produce tanning of the elatinous substanc of. theemulsions. su-ili ientto counteract the. softening .efiect. of. thesodum hydroxide. The. hydro-.quinone must be a proportion which will. giveelevated contrast to the gradation of the emulsions. The sodiumthiocyanate must. be in. an-elevated quantity.

And the sodium sulphate must be sufiicient to- Tho gr di nt or ingredints not in reased pro-- portionately would have to be in a quantity orquantities, within the specific limits which would bring about the aboveoutlined results.

The embodiments of the invention inflwhich an exclusive property orprivilege is claimed are defined as follows:

1. In a method of producing positive photographic colour images ofopaque subjects, the steps which comprise direct exposure to an opaquesubject without the medium of a color transparency of a photographicmaterial of an opaque base carrying superimposed silver halide emulsionlayers differently sensitized to blue, green and red, and containingcolour formers, subjecting the exposed material to a multi-stagedeveloping process including a first developer containing the followingingredients in the following proportions:

Water cc 1000 Sodium sulphite -grams 25- to '75 Hydro-quinone do 10 to20 Sodium thiocyanate do 2.5 to 3.5 Potassium bromide do 2.5 to 4.5Sodium hydroxide do 15 to 25 Benzotriazole do 0.65 to 0.85 Ascorbic aciddo 0.65 to 0.85 Sodium sulphate do 5 to 25 said photographic materialbeing immersed in the first developer for six minutes with thetemperature of said developer at 80 F. to increase to a high degree thesensitivity of the emulsions, immersing said material in a stop bath,simultaneously washing and subjecting said material to light exposure,further processing the material in a colour developer, washing in asecond stop bath and then removing the silver formed in the emulsionsduring the first and second developer stages.

2. In a method of producing colour positive photographic colour imagesof opaque subjects, the steps which comprise photographically producingan image of the subject on a photographic material of an opaque basecarrying superimposed silver halide emulsion layers differentlysensitized to blue, green and red, and containing colour formers,subjecting the exposed material to a multi-stage developing processincluding a first developer containing the following ingredients in thefollowing proportions:

Water cc 1000 Sodium sulphite grams 25 to 75 Hydro-quinone do 10 toSodium thiocyanate do 2.5 to 3.5 Potassium bromide do 2.5 to 4.5 Sodiumhydroxide do 15 to Benzotriazole do 0.65 to 0.85 Ascorbic acid do 0.65to 0.85 Sodium sulphate do.. 5 to 25 said photographic material beingimmersed in the first developer for six minutes with the temperature ofsaid developer at 80 F. to increase to a high degree the sensitivity ofthe emulsions.

3. A method according to claim 2, in which the benzotriazole andascorbic acid are introduced as a mixture in equal proportions of 0.75gram.

4. A method according to claim 2, in which the benzotriazole andascorbic acid are introcluced as a, mixture in proportions of from 0.65to 0.85 gram, the total quantities not exceeding 1.5 grams.

5. In a method of producing positive photographic colour images ofopaque subjects, the steps which comprise photographically producing theimage of the subject on photographic material of an opaque base carryingsuperimposed silver halide emulsion layers differently sensitized toblue, green and red, and containing colour formers, and then subjectingsaid material to a multi-stage developing process, including the firstdeveloper containing the following ingredients:

said photographic material being immersed in said developer for sixminutes with the temperature of the developer at F.

ANDRE KURT SCHWERIN.

REFERENCES CITED The following references are of record in the file ofthis patent: 1

UNITED STATES PATENTS Number Name Date 2,317,988 Forssberg r May 4, 19432,415,666 Weissberger Feb. 11, 1947 2,487,446 Kellog Nov. 8, 19492,497,917 Staufier Feb. 21, 1950 FOREIGN PATENTS Number Country Date603,121 Great Britain June 9, 1948 OTHER REFERENCES Clerc I,Photography, Pitman, N. Y., 1937, pages 80, 83.

Clerc II, Technique des Procedes Photomeehaniques, Bouzard-Calmels,Paris, vol. 1, 1947, pp. 86, 87.

Henney & Dudley, Handbook of Photography, McGraw-Hill, N. Y., 1939, pp.372, 373.

2. IN A METHOD OF PRODUCING COLOUR POSITIVE PHOTOGRAPHIC COLOUR RANGESOF OPAQUE SUBJECTS, THE STEPS WHICH COMPRISES PHOTOGRAPHICALLY PRODUCINGAN IMAGE OF THE SUBJECT ON A PHOTOGRAPHIC MATERIAL OF AN OPAQUE BASECARRYING SUPERIMPOSED SILVER HALIDE EMULSION LAYERS DIFFERENTLYSENSITIZED TO BLUE, GREEN AND RED, AND CONTAINING COLOUR FORMERS,SUBJECTING THE EXPOSED MATERIAL TO A MULTI-STAGE DEVELOPING PROCESSINCLUDING A FIRST DEVELOPER CONTAINING THE FOLLOWING INGREDIENTS IN THEFOLLOWING PROPORTIONS: